PHOENIX -- A Boston, Massachusetts man was indicted Monday by a Maricopa County grand jury for allegedly making a bomb threat against Sheriff Joe Arpaio.

Maricopa County Sheriff's deputies traveled to Massachusetts where they made contact with the suspect, Robert Paul Menard, 47. A warrant had been issued for Menard.

He's accused of threatening to bomb Arpaio's office.

That is the fourth bomb threat against Arpaio in four months, according to a spokesman for the Maricopa County Sheriff's Office.

In late July, a male suspect from Alberta, Canada threatened to brutally murder Arpaio, his wife and his children and extended family members and then bomb his home. That crime is still under investigation by the Royal Canadian Mounted Police. Deputies from the Maricopa County Sheriff's Office in Phoenix initiated the investigation and identified the suspect after intercepting an email sent by the man.

In April, a bomb capable of serious injury or death and addressed to Arpaio was intercepted by U.S. Postal authorities in Flagstaff. That investigation is ongoing by federal authorities.

In May, the new headquarters building for the Maricopa County Sheriff's Office, now under construction at 5th Avenue and Jackson Street in downtown Phoenix, was targeted by unknown persons. A threatening message was inscribed on the building indicating a bomb had been placed inside. No arrests have yet been made.

Other recent threats against Arpaio and his office not involving explosive devices have been initiated and investigated by Maricopa County Sheriff's deputies resulting in arrests and charges.

In June, Cesar Nunez, made known his intention to kill Arpaio and was tracked down by Maricopa County Sheriff's deputies. Deputies traveled to California and worked with local authorities there to charge the suspect.

In July, a Peoria, Arizona suspect, Fred Cusick, threatened to kill the Arpaio and was arrested and booked into jail.

In February, Ignacio Carbajal was arrested by MCSO deputies who tracked him to a location in Scottsdale. Carbajal threatened to travel from his family's home in Mexico to Arizona to kill Arpaio.

Those threats were motivated by Arpaio's stance on illegal immigration, according to a MCSO spokesman.

Brian Mackiewitz, lead investigator in the threats against Arpaio, said that the escalation in number and the seriousness of these recent threats lead him to believe these are, "increasingly dangerous times for Arpaio and members of this office and that all Sheriff's employees must be on the alert
and watchful."